1. Field of the Invention
The present invention concerns a method to determine as optimal a coding as possible for a flow measurement in a magnetic resonance system. The present invention also concerns a method to conduct a flow measurement with the determined optimal coding. The invention also concerns a magnetic resonance system to implement such methods.
2. Description of the Prior Art
In order to operate with as optimal a speed coding as possible in a phase contrast flow measurement conducted with a magnetic resonance system, according to the prior art time-consuming measurements must be used. If the flow coding is too strong, signal aliasing (folding) occurs in the phase contrast image, in particular in a vessel, this signal aliasing making a quantitative evaluation of the measurement data of the phase contrast flow measurement impossible. Conversely, if the flow coding is too weak, the contrast in the flow representation is too low and the precision in the flow quantification is likewise negatively affected.
According to the prior art, the following methods for determination of as optimal a flow coding as possible for a phase contrast flow measurement are known:                The optimal coding in a post-processing is determined via one or more (fast) prior measurement(s) and evaluation(s) with a coding determined beforehand. However, this is complicated and time-consuming since the flow measurement must thereby be repeated at least once, and additionally the measurement data must be loaded into a post-processing environment during the measurement workflow and be analyzed there.        In a prior measurement, phase contrast measurement data with different codings are measured in a protocol. A user visually decides in which coding only a small amount of aliasing has occurred. This coding is then defined as optimal and used in the phase contrast flow measurement for flow quantification. In addition to the likewise increased measurement effort, this method is imprecise since corresponding compromises in the spatial and temporal resolution are necessary given a use of multiple codings in a flow measurement, such that the determined optimal coding does not necessary exhibit optimal results in the actual flow measurement.        